The proposal is to study symbolic-matching-to-sample with pigeons in which the samples consist of different signal durations. Eight experiments will examine a variety of empirical questions and theoretical issues related to timing, coding, and memory for event durations. The primary aim is to compare the processing of duration signals as a function of signal modality (visual vs. auditory), signal intensity, retention interval and signal complexity (element vs compound signals). The proposed experiments will also provide a significant contribution to the current understanding of such issues as cross-modal transfer, selective attention and short-term memory. Within-subject designs will be used to assess the impact of target variables on matching-to-sample performance in pigeons; primarily when duration signals serve as samples. The designs will allow for the analysis of multiple questions concurrently, and are intended to maximize the efficiency and productivity of this research in terms of the resources and effort invested. The overall objective is to better understand representation in pigeons, which in turn contributes to the comparative study of cognition. The understanding of species differences and similarities among species in the way in which they process information is one of the most valuable contributions that can be made to our general knowledge of representation as a biological phenomenon. This knowledge can then be exploited in our attempts to understand brain-behavior relations, and to eventually comprehend the complexity of brain functioning. The benefits to human welfare from such knowledge are obvious, given that many of the most pressing behavioral problems and disorders of the brain are a direct function of what we currently do not know about the way in which the brain functions.